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Old 19th December 2011, 02:09 PM   #1
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Default input transformer - mumetal casing etc.

Dear All, investingating the possibility of building a pmillet universal PP amplifier

Push-pull KT88 class A amp with "universal" driver PCB

I researched one of the most expensive components (on the PCB that is)...the input transformer.

either a sowter or lundhal will do according to pete millet. Here is the link to the sowter product

3575

To reduce cost and shipping problems I would have liked to have all the transformer parts made and shipped through edcor electronics. I have contacted them in relation to the sowter part (to have it "cloned") and the reply is the following:

1. They don't use mumetal cans or electrostatic shielding
2. "What we can do is the 1:1 ratio PC and PCW series transformers (on our website) and could put a external copper shield on the transformer for an additional cost"

I am no engineer and would like to ask some input to some of the guys on the forum. Can such a solution work? Waht would be a good choice among the EDCOR products to emulate the charaacteristics of the sowter part?

Thanks
Alex
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Old 19th December 2011, 02:16 PM   #2
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one of the solutions might be this:

EDCOR Electronics Corporation. PCW10K/10K

or

EDCOR Electronics Corporation. WSM10K/10K

comments?

Thanks again
Alex
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Old 19th December 2011, 02:24 PM   #3
male42 is offline male42  Russian Federation
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If I understand you correctly, then the input transformer should have a screen. preferably of magnetic material. such as permalloy, nickel-containing alloys. sometimes requires a dual screen. copper in this case is not suitable.
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Old 19th December 2011, 02:26 PM   #4
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The sowter seems to have one, I guess the edcor should have one as well...

what would be the effect from using copper instead of a megnetic material?
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Old 19th December 2011, 02:31 PM   #5
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[QUOTE=Alexontherocks;2826761
what would be the effect from using copper instead of a megnetic material?[/QUOTE]

No screening from low frequency stray fields.
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Old 19th December 2011, 02:32 PM   #6
male42 is offline male42  Russian Federation
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you need to protect the transformer coil from external parasitic interference with magnetic origin. such as power transformer. Copper does not have this property
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Old 19th December 2011, 02:35 PM   #7
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Is there anyway to obtain sheets of magnetic material and have them formed to create a screen?

In conclusion you all foresee problems with using the EDCOR alternative, correct?

I have plenty of tools and machines (a friend has a CNC/metalwork shop) so forming, bending and such would not be a problem...
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Old 19th December 2011, 02:36 PM   #8
SY is offline SY  United States
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Go Cinemag. Prices are very reasonable and the quality is as good/better than Sowter. The input transformer I've been using seems identical in performance to the Jensen JT11P1 at half the price.
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Old 19th December 2011, 02:38 PM   #9
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cinemag's site seems to be down...
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Old 19th December 2011, 02:42 PM   #10
SY is offline SY  United States
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Audio Transformers By Cinemag Inc.

Came right up for me.
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